tileset: initial GPU texture atlas w/ procedural sprite painting

Signed-off-by: NotAShelf <raf@notashelf.dev>
Change-Id: I7b6991f7342362033ad72ab4700fdb9f6a6a6964

libs/tileset/tileset.h

@@ -0,0 +1,91 @@
+#ifndef TILESET_H
+#define TILESET_H
+
+#include "settings.h"
+#include <raylib.h>
+
+// Maximum number of tiles that can be registered in a single atlas
+#define MAX_TILE_ID 32
+
+// Tile IDs for map tiles (variants for visual variety)
+#define TILE_WALL_0 0
+#define TILE_WALL_1 1
+#define TILE_FLOOR_0 2
+#define TILE_FLOOR_1 3
+#define TILE_FLOOR_2 4
+#define TILE_FLOOR_3 5
+#define TILE_STAIRS_SPRITE 6
+
+// Sprite IDs for entities
+#define SPRITE_PLAYER 7
+#define SPRITE_PLAYER_WALK_0 8
+#define SPRITE_PLAYER_WALK_1 9
+#define SPRITE_PLAYER_ATTACK 10
+#define SPRITE_ENEMY_GOBLIN 11
+#define SPRITE_ENEMY_GOBLIN_WALK_0 12
+#define SPRITE_ENEMY_GOBLIN_WALK_1 13
+#define SPRITE_ENEMY_GOBLIN_ATTACK 14
+#define SPRITE_ENEMY_SKELETON 15
+#define SPRITE_ENEMY_SKELETON_WALK_0 16
+#define SPRITE_ENEMY_SKELETON_WALK_1 17
+#define SPRITE_ENEMY_SKELETON_ATTACK 18
+#define SPRITE_ENEMY_ORC 19
+#define SPRITE_ENEMY_ORC_WALK_0 20
+#define SPRITE_ENEMY_ORC_WALK_1 21
+#define SPRITE_ENEMY_ORC_ATTACK 22
+#define SPRITE_ITEM_POTION 23
+#define SPRITE_ITEM_WEAPON 24
+#define SPRITE_ITEM_ARMOR 25
+
+// Door tiles
+#define TILE_DOOR_CLOSED_SPRITE 26
+#define TILE_DOOR_OPEN_SPRITE 27
+
+// Effect/status sprites
+#define SPRITE_EFFECT_BURN 28
+#define SPRITE_EFFECT_POISON 29
+#define SPRITE_EFFECT_BLOCK 30
+#define SPRITE_SLASH_EFFECT 31
+
+// Total count of defined tiles
+#define NUM_TILE_IDS 32
+
+// Tileset encapsulates a GPU texture atlas with sub-rectangle regions per tile ID.
+// The atlas is built at startup by painting into a RenderTexture, then finalized
+// into a regular Texture2D for efficient drawing via DrawTexturePro.
+typedef struct {
+  RenderTexture2D render_target;   // RenderTexture for painting (valid before finalize)
+  Texture2D atlas;                 // GPU texture (valid after finalize)
+  int tile_w;                      // width of each tile in pixels
+  int tile_h;                      // height of each tile in pixels
+  Rectangle regions[MAX_TILE_ID];  // sub-rectangles within atlas for each tile ID
+  int tile_count;                  // number of registered tiles
+  int atlas_cols;                  // number of columns in the atlas grid
+  int atlas_rows;                  // number of rows in the atlas grid
+  int finalized;                   // 1 after tileset_finalize called, 0 otherwise
+} Tileset;
+
+// Initialize a tileset with the given tile dimensions.
+// Computes atlas grid size based on MAX_TILE_ID and allocates a RenderTexture.
+// Returns 0 on failure (e.g., RenderTexture allocation failed), non-zero on success.
+int tileset_init(Tileset *ts, int tile_w, int tile_h);
+
+// Register a tile ID with its atlas region.
+// The region is computed automatically based on tile_w/tile_h and the ID index.
+// Returns 0 if the ID is out of bounds or already registered, non-zero on success.
+int tileset_register(Tileset *ts, int id);
+
+// Finalize the tileset: converts the internal RenderTexture into a regular Texture2D
+// suitable for DrawTexturePro. After this call, painting functions must not be used.
+// Returns 0 on failure, non-zero on success.
+int tileset_finalize(Tileset *ts);
+
+// Get the atlas sub-rectangle for a given tile ID.
+// Returns a zeroed Rectangle if the ID is invalid or not registered.
+Rectangle tileset_get_region(const Tileset *ts, int id);
+
+// Destroy a tileset, unloading the atlas texture and zeroing the struct.
+// Safe to call on a zero-initialized or already-destroyed tileset.
+void tileset_destroy(Tileset *ts);
+
+#endif  // TILESET_H